The specific aims of the proposed research are to develop a target which can be used with a low energy proton accelerator as a source of epithermal neutrons for Boron Neutron Capture Therapy. The general research plan has two goals. The first goal is to base the target assembly design upon rigorous neutron transport calculations. The second goal is to construct the target assembly; and to measure, as a function of depth, for different D20 moderator thicknesses, the dose due to 10B(n, alpha ) 7Li reactions, as well as the dose to normal tissue. The Ohio State University Van de Graaff accelerator will serve as the proton accelerator for these low dose rate measurements. The results of the measurements will be compared with the predictions of calculations, and the target assembly design will be finalized. For the final target assembly design, the therapeutic gain will be determined as a function of tumor depth for the optimum target assembly moderator thickness for that tumor depth. This best therapeutic gain will be compared with therapeutic gains for reactor epithermal neutron beams.